1. Field of Invention
This invention pertains to applications for bladder securement mechanisms for a tire press utilizing a position sensor mechanism, and more specifically to a method for relieving pressure in a newly vulcanized tire that is still in the tire press, and even more specifically to a method for more safely opening a tire press in the event a bladder has ruptured.
2. Description of the Related Art
Tire presses and methods for making tires are well known in the art. FIG. 2 shows a green tire 12 undergoing a curing process in a tire press 10. The green tire 12 is placed within a cavity defined by a lower mold 14 and an upper mold 16. The lower mold 14 is fixedly installed on a base frame 18. The upper mold 16 can be closed and opened in relation to the lower mold 14. In FIG. 2, the tire press 10 is shown in the closed position.
A bladder securement mechanism 40, some aspects of which are currently known in the art, is illustrated in FIG. 1. The bladder securement mechanism 40 is commonly referred to as a xe2x80x9ccenter mechanism.xe2x80x9d In the bladder securement mechanism 40, a center mechanism tube 42 is supported by a guide cylinder 44, which is fixed on the base frame 18. The upper end 32 of a bladder 30 is held by an upper clamping mechanism 70, which is attached to the upper end 48 of a center mechanism rod 46. The center mechanism rod 46 is positioned on a piston 50 of the center mechanism tube 42. A lower clamping mechanism 80, which holds the lower end 34 of the bladder 30, is attached to the upper end of the center mechanism tube 42 through a hub 51. A pressurized fluid is supplied by way of a first port 52 formed in the lower part of the center mechanism tube 42 to a portion below the piston 50. The pressurized fluid is also supplied from a second port 54 through a pipe 56 to a portion on the top of the piston 50. The pipe 56 passes through the piston 50 and is inserted into the center mechanism rod 46.
The piston 50 and the center mechanism rod 46 move upward together. When the bladder 30 is deformed around the lower clamping mechanism 80, a heated pressurized medium such as steam is supplied through a fluid supply tube 58 via a through hole on the hub side into the bladder 30. Then the bladder 30 comes tightly into contact with the inner side of the green tire 12.
A floating piston 60 is adapted to contact the hub 51 and is slidably attached to the center mechanism rod 46. A stacking spacer 62 is positioned above the floating piston 60, and a stretch height spacer 64 is positioned below the floating piston 60 but above the piston 50. The stacking spacer 62 and the stretch height spacer 64 are exchangeably attached to the outside of the center mechanism rod 46. The stacking spacer 62 sets the lower limit position of the upper clamping mechanism 70 so that the upper clamping mechanism 70 is set to a shaping height corresponding to the tire size. The stretch height spacer 64 limits the upper clamping mechanism""s 70 upward movement.
While suited for their intended purpose, present bladder securement mechanism designs of the tire curing presses have the following disadvantages. As different sized tires are cured, the top clamping ring of the upper clamping mechanism must be repositioned to accommodate each tire size. This requires spacers of different lengths to be changed on the bladder securement mechanism. These spacers are cumbersome to change as different sized tires are cured. In addition, valuable production time is wasted. Also, since the spacers are generally fabricated from standard pipe, their lengths are not as precise as desired. Further, the spacers are subject to wear and tear over time, which leads to further imprecision and, thereby, possible imprecision in the tire.
Another problem with traditional spacers is that adjustment of the top ring is extremely limited during the curing process because the top clamping ring cannot advance towards the bottom ring once it has contacted the spacer. Still yet, another disadvantage of utilizing spacers is that the tire press only has two positions: open and closed. There is no mechanism for fine precision to ensure the green tire will cure correctly without any flaws or inaccuracies.
Present bladder securement mechanisms are limited in performance due to the restrictive nature of the spacers. For example, the tire press utilizes a variety of pressure sensors to ensure that it is safe to open the press. If pressure sensors indicate excess pressure in the tire press, the tire press cannot open. Currently, there is no way to detect pressure between the bladder and the vulcanized tire that is still in the press. If a defect in the bladder causes the pressure medium to pass therethrough and into the tire, there is no way to detect the pressure. Since all pressure sensors would appear to show normal pressure in the tire press, the press can be opened. This could result in the excess pressure being directed toward the tire press operator, which is undesirable. Even if the excess pressure was detected, there is no way to release it with the press closed due to the presence of the spacers in the bladder securement mechanism.
Therefore, a need exists in the art for a bladder securement mechanism that operates without a spacer and that overcomes the foregoing difficulties and others. The present invention is contemplated to overcome these disadvantages by utilizing a linear position sensor mechanism with the bladder securement mechanism, such that the upper clamping mechanism may be moved at any time during the curing process. Having the ability to move the upper clamping mechanism offers safety and tire forming advantages.
The present invention is a method for relieving pressure in a vulcanized tire while still in a tire press. A tire press comprises a lower mold, an upper mold, and a bladder securement mechanism. The bladder securement mechanism has an upper clamping mechanism for securing the upper periphery of a bladder and a lower clamping mechanism for securing the lower periphery of the bladder. A center mechanism tube has a center mechanism rod positioned therein. A piston is disposed within the center mechanism tube. The piston provides reciprocating motion to the center mechanism rod. A position sensor mechanism is operatively associated with the bladder securement mechanism. The method comprises the steps of positioning a green tire on the bottom mold; lowering the upper clamping mechanism; inflating the bladder, thereby forming a seal between the bladder and the tire; closing the press so that the green tire is enclosed within the upper and lower molds; curing the green tire; breaking the seal; releasing pressure from the tire; and, dissipating the released pressure. Accordingly, it is an object of the present invention to provide a method for directing excess pressure captured in a newly vulcanized tire away from the operator and into the tire press structure.
Another object of the present invention is to provide a method for relieving pressure in a vulcanized tire while still in a tire press, wherein the position sensor mechanism comprises a linear sensing rod disposed in the center tube; a magnet positioned within the piston, the magnet being laterally spaced from the linear sensing rod, and a signal generating unit for determining the travel distance of the piston.
Yet, another object of the present invention is to provide a method for relieving pressure in a vulcanized tire while still in a tire press further comprising the steps of moving the magnet with the piston; determining the displacement of the piston relative to the bottom of the center tube; and, controlling the vertical movement of the upper clamping mechanism.
Further, another object of the present invention is to provide a method for relieving pressure in a vulcanized tire while still in a tire press, wherein breaking the seal comprises the step of moving the upper clamping mechanism downward.
Still yet, another object of the present invention is to provide a method for relieving pressure in a vulcanized tire while still in a tire press, wherein moving the upper clamping mechanism further comprises the step of moving the upper clamping mechanism vertically at any time during the curing cycle to release excess pressure.
Another object of the present invention is to provide a method for relieving pressure in a vulcanized tire while still in a tire press, wherein the released pressure is contained within the tire press.
Further, another object of the present invention is to provide a method for relieving pressure in a vulcanized tire while still in a tire press wherein the released pressure in contained in a void defined by a press beam and a mold actuating ring.
Still other benefits and advantages of the invention will become apparent to those skilled in the art to which it pertains upon a reading and understanding of the following detailed specification.